Isostatic press

ABSTRACT

A HYDRAULIC PRESS IN WHICH THE PRESSURE CHAMBER FOR ISOSTATIC MOLDS AND LIQUID COMPRISES AN ANNULAR PISTON HAVING ITS LOWER END TELESCOPED OVER A STATIONARY PISTON. THE UPPER END OF THE ANNULAR PISTON IS HELD IN SEALING ENGAGEMENT WITH THE MAIN PISTON WHICH PRESSURIZED THE LIQUID AND THE MOLDS BY FORCING THE ANNULAR PISTON DOWN OVER THE STATIONARY PISTON.

Nmr. 9, 1971 m. RIETMANN 3,518,164

ISOSTATIC PRESS Filed May 25, 1970 2 Sheets-Sheet 1 M {jNVENTO/i. BY 7 a (Li/(m Nov. 9., 191 N. RIETMANN 3,513,164

ISOSTATIC PRESS Filed May 25, W70 2 Sheets-Sheet 3 INVENTOR.

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United States 3,618,164 ISOSTATIQ PRESS Norman lRietmann, Erie, Pa., assignor to Autoclave Engineers, Inc., Erie, lPa. lFiled May 25, 1970, Ser. No. 40,290 Int. Cl. 1330b /00, 11/00 US. Cl. 18-5 H Claims ABSTRACT OF THE DISCLOSURE This invention is a press for isostatically pressing powdered metals, ceramics and the like, in which the pressure chamber for the molds containing the powder to be compressed is at the center of an annular piston having its lower end telescoped over a stationary piston. As the annular piston is forced downward by the main piston, the length of the pressure chamber is decreased and the liquid within the chamber is pressurized to compact the powders within the molds.

In the drawing, FIG. 1 is a sectional elevation of the press in its open position and FIG. 2 is a similar view of the press in its closed position.

In the open position of the press, a double acting main or power piston 1 is raised by fluid pressure supplied from line 2 through three-way valve 3. The fluid pressure is supplied to an annular chamber 4 surrounding the reduced diameter end 5 of the piston. The chamber is closed at its upper end by the enlarged end or head 6 of the piston and is closed at its lower end by the inwardly extending annular wall 8 of the main cylinder 7. Suitable packing 9 seals the joint between the piston and the wall 8. As the piston moves upward, the liquid between the head 6 and the closed upper end of the cylinder 7 is forced out through three-way valve 10 into a discharge line 11.

In the open position, an annular piston 12 is urged upward by fluid pressure in an annular chamber 13 between a stationary piston or plunger 14 and the bore of a lower cylinder 15. Fluid pressure for the chamber 13 is supplied from a line 16 through a relief valve 17 which maintains constant pressure in the chamber at all times. The upper end of the stationary piston 14 extends within the bore 18 of the annular piston 12. Packing 19 makes sealing engagement between the bore 18 and the stationary piston 14 and similar packing 20 makes sealing engagement between the cylinder and the outer surface of the piston 12. In the open position of the press, a lug 21 on the piston 12 engages a stop 21a which limits the upward movement of the piston. The entire space of the bore 18 above the stationary piston 14 constitutes a pressure chamber 22 which is available for loading with the usual isostatic elastomeric molds containing powders to be cornpressed. These molds are usually loaded in a wire basket. The molds and the basket are well known items which need not be illustrated.

After the press has been loaded with the desired molds, the pressure chamber 22 is filled with liquid through way 23 in piston 14 through valve 23a in line 23b. After the pressure chamber is filled with liquid, the valve 23a is closed. The main piston 1 is then lowered by turning valve 3 to drain liquid from the chamber 4 and by turning valve 10 to supply liquid under pressure from line 24 to the space between the upper end of cylinder 7 and piston head 3,018,164 Patented Nov. 9, 1971 6. This moves the main piston 1 downward and causes the lower end of the main piston to engage the upper end of the annular piston 12 and force it downward over the stationary piston 14. Leaking between the main piston and the annular piston 12 is prevented by a seal 25 which is held in sealing engagement with the lower end of the main piston by the pressure of the liquid in chamber 13 acting on the lower end of the annular piston 12. As the main piston moves downward, the length of the pressure chamber 22 is decreased and since the liquid in the chamber is virtually incompressible, causes hydraulic pressure to be uniformly applied over the entire exterior surface of the molds to compact the powders. At the end of the pressure stroke shown in FIG. 2, the powders in the molds have been compacted.

The normal operating pressure developed in the pressure chamber 22 is in the range of 5000 p.s.i. to over 100,000 p.s.i. The maximum compacting pressure that can be achieved is limited only by the strength of the material used in the manufacture of the machine and is not limited by the design concept itself in any manner.

The pressure build up in the pressure chamber is directly related to the force applied by the main ram. The greater the force by the main ram, the greater the pressure build up in the pressure chamber.

The press is opened by moving valve 23a to the position draining the pressure chamber 22 through line 26, by moving valve 10 to the position draining the space between the piston head 6 and the upper end of cylinder 7 through line 11 and moving valve 3 to the position supplying liquid pressure to the chamber 4 causing the main piston 1 to be moved upward. The annular piston 12 follows the main piston until stopped by engagement of lug 21 with stop 21a in position for unloading the molds.

What is claimed is:

1. An isostatic press comprising an annular piston having a bore closed at its lower end by the upper end of a stationary piston in telescoping relation to the lower end of said bore, the bore of the annular piston above the stationary piston serving as a pressure chamber for isostatic pressure molds and liquid surrounding the molds, means for biasing said annular piston upward against a stop means, and means for pressurizing the liquid in said chamber by means sealing the upper end of said bore and forcing the annular piston downward over the stationary piston to decrease the length of the pressure chamber.

2. The press of claim 1 in which the means for biasing the annular piston upward comprises a cylinder surrounding the lower end of the annular piston and means for supplying a constant pressure fluid to the cylinder below the lower end of the annular piston.

3. The press of claim 1 in which the stationary piston has a conduit leading to its upper end for supplying liquid to and draining liquid from said chamber.

4. The press of claim 1 in which the means for force ing the annular piston downward comprises a hydraulic piston having a lower surface engaging the upper end of the annular piston.

5. The press of claim 4 in which the sealing means comprises a sealing element between said lower surface and the upper end of the annular piston.

6. The press of claim 2 in which the sealing means comprises a sealing element on the upper end of the annular piston.

7. The press of claim 2 in which the constant pressure fluid is supplied through a relief valve.

8. The press of claim 2 in which the stationary piston has a conduit leading to its upper end for supplying liquid to and draining liquid from said chamber.

9. The press of claim 8 in which the means for forcingthe annular piston downward comprises a hydraulic piston having a lower surface engaging the upper end of the annular piston.

10. The press of claim 9 in which the sealing means comprises a sealing element between said lower surface and the upper end of the annular piston. 5

References Cited UNITED STATES PATENTS 4 Bauer 18--16 R X Levey 18-16 R Bobrousky 18 HIPRES DIG Bouis et a1 18-165 X Fuchs 18 HIPRES DIG Boyer et a1 185 H X J. HOWARD FLINT, 111., Primary Examiner US. Cl. X.R. 

